Best way to repair this concrete spalling (cancer)?

Discussion in 'Repairs & Maintenance' started by Depreciator, 5th Dec, 2018.

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  1. Depreciator

    Depreciator Well-Known Member

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    It's a strata repair, but I am not confident the person they have contracted to do the job has done this sort of thing before so I want to guide them on exactly how to do it and what products to use.
    Not a huge job, but one that needs to be done properly.
    Scott
     

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  2. bashworth

    bashworth Well-Known Member

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    I have generally found xypex products (xypex repair) one of the best solutions for concrete repair.

    They have a range of products with comprehensive instructions.
     
  3. robboat

    robboat Well-Known Member

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    Had a problem with concrete cancer in sunny Perth a few years ago....just poor construction and no sealing at Sth Perth.
    @Depreciator - where is this property? Exposed to any salt air?
    Hard to tell from the one pic....
    Fix the cause...
    Is that corner supporting the whole brick wall? Cantilever?
    It looks like insufficient concrete cover to the steel.
    Also, the steel mesh could have been damaged at that corner during construction.
    Check for hairline cracking in this area and water being trapped behind the brick wall.
    Repair properly.
    It's not a big job but needs to be done correctly.
    If possible - would cut the mesh back to clean metal.
    Drill holes to accomodate new steel rods.
    Chemiweld these rods into the existing good concrete.
    Use steel primer on exposed rods.
    I used Ardex concrete repair product - ARDEX BR 340 - Structural Concrete Patching and Repair Mortar
    They also have injection products for cracks.....
    Follow the instructions accurately.....takes time.
    Allow for complete curing time....+1m...keep protected from the elements
    Use concrete sealer and recheck waterproofing of area.

    Good luck...
     
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  4. Scott No Mates

    Scott No Mates Well-Known Member

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    Not sure why there's a cranked bar but it is what it is. Insufficient cover is the cause. Need to cut out and replace the rusted bar with some galvanised bar, cut out much more of the concrete, drill (probably 300 mm) and chemset bar into sound concrete. Patch concrete as above.

    Note that there is a flashing under that external brick as well.
     
  5. Depreciator

    Depreciator Well-Known Member

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    It's in Sydney's inner west, so no salt air.
    The building was built in the late 60s, I think.
    Yes, the slab is a cantilever and the blond brick wall is the side of the building.
    The quote to repair was $1,500, but that was just a clean-up, Rust Guard on the rod and a patch. I knew the scope of works was insufficient - and the quote too high for those works.
    The quote might be okay if the job is done properly as advised above.
    Thanks for the responses.
     
  6. willair

    willair Well-Known Member Premium Member

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    Maybe one would form-work the corner section and set a pillar into the ground but that would maybe be over-kill,but if it's counter lever set-up and a ppor I would do the formwork ,but cost wise the $1500 would also do the same end effect..imho..i'm not a form-worker ..
     
  7. norwoodman

    norwoodman Well-Known Member

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    Need to be careful with applying repairs in these sorts of cantilevered slabs. you'll want a mortar product that has strong bonding to the existing concrete and steel reinforcing bars, otherwise the repaired corner will drop off over time. The rebar detailing is strange, normally there should be L-bars reinforcing at the corners rather than a cranked bar.
     
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